Handle None in first.
Handle removed files in PollingMonitor.
Add tests for first and notes on missing tests.
Update TODOs.
Test PollingMonitor.
 - Add monitor and stop methods to abstract Monitor definition as doc.
 - Add stop machinery to PollingMonitor.
 - Add initial PollingMonitor tests.
 - Add Monfile for our own development.
 - Update Monfile to use concise notation.
 - Ensure names are lists.
 - Removed redundant group stuff.